The present invention relates to drawing of elongated stock, such as copper tubing and using a drawing die, a rotating drum with clamp for drawing the tubing through the die.
Equipment of this type is constructed, for example, as to the following detail. In the so-called bull blocks, the tubing (or other elongated stock) is held by clamps throughout the drawing and is released only upon completion. The length of the drawn stock is limited here by circumferential and axial dimensions of the drawing drum.
The so-called spinner block differs from a bull block in that the stock is severed from the holding clamp after a few loops have been wound on the drum and frictional engagement of the drum by the loops provides for further pulling. The drum is vertically arranged and a disk pushes the loops down so that they drop into a container. Of course, a plurality of loops is always on the drum to provide for the necessary drawing force. It can thus be seen that this spinner block permits basically the processing of endless tubing.
Therefore, the bull block arrangement will be used for drawing e.g. tubes which are relatively light and short, so that all of it can be wound on the drum without having to provide for an excessively large (and heavy!) drum. One could wind tubing in two layers, but that is not too desirable, as the loops may become intertwined.
The spinner block has the added advantage of higher speed, but one has to start quite slowly, until, say, seven to nine loops have been wound, and they must be held against the periphery of the drum by rolls and to ensure transition of pulling by the clamp to pulling by frictional engagement when the end has been severed from the clamp.